Spatial Light Modulating (SLM) systems include Digital Light Processing™ (DLP™) systems. DMD and DLP™ are trademarks of Texas Instruments Corporation. Recent developments in SLM technology rely on SLM elements that provide diamond shaped pixels instead of square shaped pixels. Processing techniques for SLM systems include a so called “smooth pixel” processing technique. According to the smooth pixel technique, a displayed image is formed by combining a first set of pixels with a second set of pixels. The second set is displaced from the first set. The combined first and second sets form a displayed image.
In one example SLM system, an array of SLM elements provides first and second pixel sets for each incoming picture, or frame, to be displayed. The combined pixels from the first and second pixel sets provide more displayed pixels than the number of SLM elements in the array.
However, a drawback is associated with this technique. Pixels of the first set effectively overlap pixels from the second set in the displayed image. As a result, light in the regions of overlapping pixels is a combination of light from each of the overlapping pixels. This sometimes results in brighter than intended, or less bright than intended image portions. To address this issue commonly assigned co-pending application no. PCT/US2005/09621 filed on Mar. 22, 2005 by common inventor Rumreich describes an inventive filter and method to counter the effects of overlapping pixel brightness. Applicants' inventive filter has been found to improve images provided by smooth pixel type display systems.
With pixel brightness filtering techniques, any brightness change to the pixel, or gain applied to the pixel during brightness processing of the pixel, can cause the resulting pixel intensity to exceed the maximum value of which the display is capable. In that case, values exceeding the maximum value are typically clipped, for example by a limiter circuit, at the maximum value. Clipping the pixel output intensity to this maximum value creates false contours and other artifacts since some of the intensity information is lost. Therefore, circuits and methods to allow pixel brightness processing to enhance image quality, while at the same time minimizing clipping, are needed.